Operant baseline procedures suppress infant social behavior

Two groups of six 3-month-old infants participated in a study which contained four consecutive 2-min periods. During Periods 2 and 4 both groups received adult social stimulation on the same prearranged schedule. The treatments during Periods 1 and 3 differed between the two groups; no adult was present for the A-S group, while the B-S group received the typical operant baseline (unresponsive adult treatment) for these two periods. Social stimulation caused a significant increase in vocal rate from the preceding control period for both groups. Infants in the A-S group vocalized at the same rate during the two periods in which the adult was absent and at similar rates during the two stimulation periods. For infants in the B-S group, baseline procedures suppressed vocal rates and did not provide a neutral or operant level of responding with which the effects of social conditioning could be compared.